Detector arrangements included in electric arrangements of the above-disclosed type are common in the art. As a rule, such arrangements are included in every apparatus fitted with an electrically driven motor. The drawback inherent in these prior art arrangements is that they display detector means which are connected to the switch and which, after having registered a change of switch position across a separate conductor convey this change to the control circuit included. This separate conductor is normally difficult to mount in place since it is often a matter of very small and unstable parts which must be connected together, and there is therefore a serious risk that mounting in place will not be satisfactory, which easily results in the apparatus ceasing to function.